1. Field of the Invention
The present invention relates to manufacturing processes for electronic modules composed of a plurality of substrates. In particular, the present invention provides a method for manufacturing high performance, high reliability modules (e.g. RF) which utilizes an alignment plate with shims, or the like, for allowing the alignment and assembly of the substrates to be performed in a repeatable and more precise manner.
2. Background of the Invention
Contract awards for high performance, high reliability RF modules are very competitive. Not only are developmental costs being challenged, but the recurring manufacturing costs as well are being challenged. Unique design and process enablers create a market edge, therefore, it is desirable to continually seek out and develop process enhancements which reduce manufacturing costs while simultaneously improving quality.
Two contributors to manufacturing cost are build and test labor. As the complexity of one of these factors increases, usually the other follows. Any variation in the materials and manufacturing processes drives up the test time and in turn the cost. But if an electronic module can be built the same way each time, then it can be tested the same way. Typical build processes for modules are as follows: substrate attach, component attach, and interconnect. Automated equipment and tooling is commonly used to reduce build variation of component attach and interconnect. Additionally, the substrate technology and substrate attach process are dependent on a manufacturer's packaging of the overall RF module design.
A common approach for manufacturing high reliability, high performance RF modules is to attach ceramic substrates into a hermetic sealed housing. The variables that influence the RF performance of this approach are substrate artwork alignment, substrate-to-substrate gaps, and substrate-to-substrate height. Also, a tool is needed to control these variables.
For example, in a typical prior art substrate attach build for RF designs, a precut adhesive film or preform is placed on the floor of the case and substrates are placed on top of it. Each substrate is located one at a time to align the RF lines and provide a minimum gap around each substrate. Another substrate attach process for prior art RF module designs typically uses adhesive paste and shims. The paste and shims are dispensed or manually applied to the housing floor. Next, one or more substrates are placed, one at a time, onto the paste. Each substrate is scrubbed into the paste to promote wetting. Shims are then placed between substrates to create the proper gap. The sides of the substrates are also shimmed to the housing walls so as to align the artworks. After curing, the shims may be removed and any required cleaning is performed.
The aforementioned processes have some disadvantages which could be improved upon. In particular, the alignment is operator dependent; that is to say, the manual placement, alignment and shimming process increases variance in alignment repeatability. Furthermore, manual placement, alignment and shimming is labor intensive.
It would be advantageous and desirable to provide a tool and method of using the tool that could repetitively and accurately pre-align and gap RF substrates utilizing an adhesive film or tape rather than paste. Ideally, a tool, jig or alignment plate could be provided which would move the substrate alignment task away from the preform. As a result of utilizing an alignment plate, the placement and alignment process becomes a repeatable process, while the shimming portion of the process is entirely eliminated, except for during the fabrication of the alignment plate.